Replace penultimate naming with proximal (#13460)

Summary:
With generalized age-based tiering (work-in-progress), the "warm tier" data will no longer necessarily be placed in the second-to-last level (also known as the "penultimate level").

Also, the cold tier may no longer necessarily be at the last level, so we need to rename options like `preclude_last_level_seconds` to `preclude_cold_tier_seconds`, but renaming options is trickier because it can be a breaking change for consuming applications. We will do this later as a follow up.

**Minor fix included**: Fixed one `use-after-move` in CompactionPicker

Pull Request resolved: #13460

Test Plan: CI

Reviewed By: pdillinger

Differential Revision: D71059486

Pulled By: jaykorean

fbshipit-source-id: fd360cdf719e015bf9f9e3f6f1663438226566a4

Author: jaykorean

db/compaction/compaction.cc

@@ -338,16 +338,16 @@ Compaction::Compaction(
                   _blob_garbage_collection_age_cutoff > 1
               ? mutable_cf_options().blob_garbage_collection_age_cutoff
               : _blob_garbage_collection_age_cutoff),
-      penultimate_level_(
-          // For simplicity, we don't support the concept of "penultimate level"
+      proximal_level_(
+          // For simplicity, we don't support the concept of "proximal level"
           // with `CompactionReason::kExternalSstIngestion` and
           // `CompactionReason::kRefitLevel`
           _compaction_reason == CompactionReason::kExternalSstIngestion ||
                   _compaction_reason == CompactionReason::kRefitLevel
               ? Compaction::kInvalidLevel
-              : EvaluatePenultimateLevel(vstorage, mutable_cf_options_,
-                                         immutable_options_, start_level_,
-                                         output_level_)) {
+              : EvaluateProximalLevel(vstorage, mutable_cf_options_,
+                                      immutable_options_, start_level_,
+                                      output_level_)) {
   MarkFilesBeingCompacted(true);
   if (is_manual_compaction_) {
     compaction_reason_ = CompactionReason::kManualCompaction;
@@ -405,10 +405,10 @@ Compaction::Compaction(
     }
   }
 
-  PopulatePenultimateLevelOutputRange();
+  PopulateProximalLevelOutputRange();
 }
 
-void Compaction::PopulatePenultimateLevelOutputRange() {
+void Compaction::PopulateProximalLevelOutputRange() {
   if (!SupportsPerKeyPlacement()) {
     assert(keep_in_last_level_through_seqno_ == kMaxSequenceNumber);
     return;
@@ -417,46 +417,42 @@ void Compaction::PopulatePenultimateLevelOutputRange() {
   // exclude the last level, the range of all input levels is the safe range
   // of keys that can be moved up.
   int exclude_level = number_levels_ - 1;
-  penultimate_output_range_type_ = PenultimateOutputRangeType::kNonLastRange;
+  proximal_output_range_type_ = ProximalOutputRangeType::kNonLastRange;
 
-  // For universal compaction, the penultimate_output_range could be extended if
-  // all penultimate level files are included in the compaction (which includes
-  // the case that the penultimate level is empty).
+  // For universal compaction, the proximal_output_range could be extended if
+  // all proximal level files are included in the compaction (which includes
+  // the case that the proximal level is empty).
   if (immutable_options_.compaction_style == kCompactionStyleUniversal) {
     exclude_level = kInvalidLevel;
-    penultimate_output_range_type_ = PenultimateOutputRangeType::kFullRange;
-    std::set<uint64_t> penultimate_inputs;
+    proximal_output_range_type_ = ProximalOutputRangeType::kFullRange;
+    std::set<uint64_t> proximal_inputs;
     for (const auto& input_lvl : inputs_) {
-      if (input_lvl.level == penultimate_level_) {
+      if (input_lvl.level == proximal_level_) {
         for (const auto& file : input_lvl.files) {
-          penultimate_inputs.emplace(file->fd.GetNumber());
+          proximal_inputs.emplace(file->fd.GetNumber());
         }
       }
     }
-    auto penultimate_files = input_vstorage_->LevelFiles(penultimate_level_);
-    for (const auto& file : penultimate_files) {
-      if (penultimate_inputs.find(file->fd.GetNumber()) ==
-          penultimate_inputs.end()) {
+    auto proximal_files = input_vstorage_->LevelFiles(proximal_level_);
+    for (const auto& file : proximal_files) {
+      if (proximal_inputs.find(file->fd.GetNumber()) == proximal_inputs.end()) {
         exclude_level = number_levels_ - 1;
-        penultimate_output_range_type_ =
-            PenultimateOutputRangeType::kNonLastRange;
+        proximal_output_range_type_ = ProximalOutputRangeType::kNonLastRange;
         break;
       }
     }
   }
 
-  // FIXME: should make use of `penultimate_output_range_type_`.
+  // FIXME: should make use of `proximal_output_range_type_`.
   // FIXME: when last level's input range does not overlap with
-  //  penultimate level, and penultimate level input is empty,
-  //  this call will not set penultimate_level_smallest_ or
-  //  penultimate_level_largest_. No keys will be compacted up.
-  GetBoundaryInternalKeys(input_vstorage_, inputs_,
-                          &penultimate_level_smallest_,
-                          &penultimate_level_largest_, exclude_level);
-
-  if (penultimate_output_range_type_ !=
-      PenultimateOutputRangeType::kFullRange) {
-    // If not full range in penultimate level, must keep everything already
+  //  proximal level, and proximal level input is empty,
+  //  this call will not set proximal_level_smallest_ or
+  //  proximal_level_largest_. No keys will be compacted up.
+  GetBoundaryInternalKeys(input_vstorage_, inputs_, &proximal_level_smallest_,
+                          &proximal_level_largest_, exclude_level);
+
+  if (proximal_output_range_type_ != ProximalOutputRangeType::kFullRange) {
+    // If not full range in proximal level, must keep everything already
     // in the last level there, because moving it back up might cause
     // overlap/placement issues that are difficult to resolve properly in the
     // presence of range deletes
@@ -486,53 +482,53 @@ Compaction::~Compaction() {
 }
 
 bool Compaction::SupportsPerKeyPlacement() const {
-  return penultimate_level_ != kInvalidLevel;
+  return proximal_level_ != kInvalidLevel;
 }
 
-int Compaction::GetPenultimateLevel() const { return penultimate_level_; }
+int Compaction::GetProximalLevel() const { return proximal_level_; }
 
 // smallest_key and largest_key include timestamps if user-defined timestamp is
 // enabled.
-bool Compaction::OverlapPenultimateLevelOutputRange(
+bool Compaction::OverlapProximalLevelOutputRange(
     const Slice& smallest_key, const Slice& largest_key) const {
   if (!SupportsPerKeyPlacement()) {
     return false;
   }
 
-  // See FIXME in Compaction::PopulatePenultimateLevelOutputRange().
+  // See FIXME in Compaction::PopulateProximalLevelOutputRange().
   // We do not compact any key up in this case.
-  if (penultimate_level_smallest_.size() == 0 ||
-      penultimate_level_largest_.size() == 0) {
+  if (proximal_level_smallest_.size() == 0 ||
+      proximal_level_largest_.size() == 0) {
     return false;
   }
 
   const Comparator* ucmp =
       input_vstorage_->InternalComparator()->user_comparator();
 
   return ucmp->CompareWithoutTimestamp(
-             smallest_key, penultimate_level_largest_.user_key()) <= 0 &&
+             smallest_key, proximal_level_largest_.user_key()) <= 0 &&
          ucmp->CompareWithoutTimestamp(
-             largest_key, penultimate_level_smallest_.user_key()) >= 0;
+             largest_key, proximal_level_smallest_.user_key()) >= 0;
 }
 
 // key includes timestamp if user-defined timestamp is enabled.
-void Compaction::TEST_AssertWithinPenultimateLevelOutputRange(
+void Compaction::TEST_AssertWithinProximalLevelOutputRange(
     const Slice& user_key, bool expect_failure) const {
 #ifdef NDEBUG
   (void)user_key;
   (void)expect_failure;
 #else
   assert(SupportsPerKeyPlacement());
 
-  assert(penultimate_level_smallest_.size() > 0);
-  assert(penultimate_level_largest_.size() > 0);
+  assert(proximal_level_smallest_.size() > 0);
+  assert(proximal_level_largest_.size() > 0);
 
   auto* cmp = input_vstorage_->user_comparator();
 
   // op_type of a key can change during compaction, e.g. Merge -> Put.
-  if (!(cmp->Compare(user_key, penultimate_level_smallest_.user_key()) >= 0)) {
+  if (!(cmp->Compare(user_key, proximal_level_smallest_.user_key()) >= 0)) {
     assert(expect_failure);
-  } else if (!(cmp->Compare(user_key, penultimate_level_largest_.user_key()) <=
+  } else if (!(cmp->Compare(user_key, proximal_level_largest_.user_key()) <=
                0)) {
     assert(expect_failure);
   } else {
@@ -1018,7 +1014,7 @@ uint64_t Compaction::MinInputFileEpochNumber() const {
   return min_epoch_number;
 }
 
-int Compaction::EvaluatePenultimateLevel(
+int Compaction::EvaluateProximalLevel(
     const VersionStorageInfo* vstorage,
     const MutableCFOptions& mutable_cf_options,
     const ImmutableOptions& immutable_options, const int start_level,
@@ -1033,21 +1029,21 @@ int Compaction::EvaluatePenultimateLevel(
     return kInvalidLevel;
   }
 
-  int penultimate_level = output_level - 1;
-  assert(penultimate_level < immutable_options.num_levels);
-  if (penultimate_level <= 0) {
+  int proximal_level = output_level - 1;
+  assert(proximal_level < immutable_options.num_levels);
+  if (proximal_level <= 0) {
     return kInvalidLevel;
   }
 
-  // If the penultimate level is not within input level -> output level range
-  // check if the penultimate output level is empty, if it's empty, it could
-  // also be locked for the penultimate output.
+  // If the proximal level is not within input level -> output level range
+  // check if the proximal output level is empty, if it's empty, it could
+  // also be locked for the proximal output.
   // TODO: ideally, it only needs to check if there's a file within the
   //  compaction output key range. For simplicity, it just check if there's any
-  //  file on the penultimate level.
+  //  file on the proximal level.
   if (start_level == immutable_options.num_levels - 1 &&
       (immutable_options.compaction_style != kCompactionStyleUniversal ||
-       !vstorage->LevelFiles(penultimate_level).empty())) {
+       !vstorage->LevelFiles(proximal_level).empty())) {
     return kInvalidLevel;
   }
 
@@ -1061,7 +1057,7 @@ int Compaction::EvaluatePenultimateLevel(
     return kInvalidLevel;
   }
 
-  return penultimate_level;
+  return proximal_level;
 }
 
 void Compaction::FilterInputsForCompactionIterator() {

db/compaction/compaction.h

@@ -102,13 +102,13 @@ class Compaction {
                  BlobGarbageCollectionPolicy::kUseDefault,
              double blob_garbage_collection_age_cutoff = -1);
 
-  // The type of the penultimate level output range
-  enum class PenultimateOutputRangeType : int {
-    kNotSupported,  // it cannot output to the penultimate level
-    kFullRange,     // any data could be output to the penultimate level
+  // The type of the proximal level output range
+  enum class ProximalOutputRangeType : int {
+    kNotSupported,  // it cannot output to the proximal level
+    kFullRange,     // any data could be output to the proximal level
     kNonLastRange,  // only the keys within non_last_level compaction inputs can
-                    // be outputted to the penultimate level
-    kDisabled,      // no data can be outputted to the penultimate level
+                    // be outputted to the proximal level
+    kDisabled,      // no data can be outputted to the proximal level
   };
 
   // No copying allowed
@@ -370,29 +370,29 @@ class Compaction {
 
   Slice GetLargestUserKey() const { return largest_user_key_; }
 
-  PenultimateOutputRangeType GetPenultimateOutputRangeType() const {
-    return penultimate_output_range_type_;
+  ProximalOutputRangeType GetProximalOutputRangeType() const {
+    return proximal_output_range_type_;
   }
 
   // Return true if the compaction supports per_key_placement
   bool SupportsPerKeyPlacement() const;
 
-  // Get per_key_placement penultimate output level, which is `last_level - 1`
+  // Get per_key_placement proximal output level, which is `last_level - 1`
   // if per_key_placement feature is supported. Otherwise, return -1.
-  int GetPenultimateLevel() const;
+  int GetProximalLevel() const;
 
-  // Return true if the given range is overlap with penultimate level output
+  // Return true if the given range is overlap with proximal level output
   // range.
   // Both smallest_key and largest_key include timestamps if user-defined
   // timestamp is enabled.
-  bool OverlapPenultimateLevelOutputRange(const Slice& smallest_key,
-                                          const Slice& largest_key) const;
+  bool OverlapProximalLevelOutputRange(const Slice& smallest_key,
+                                       const Slice& largest_key) const;
 
-  // For testing purposes, check that a key is within penultimate level
+  // For testing purposes, check that a key is within proximal level
   // output range for per_key_placement feature, which is safe to place the key
-  // to the penultimate level. Different compaction strategies have different
+  // to the proximal level. Different compaction strategies have different
   // rules. `user_key` includes timestamp if user-defined timestamp is enabled.
-  void TEST_AssertWithinPenultimateLevelOutputRange(
+  void TEST_AssertWithinProximalLevelOutputRange(
       const Slice& user_key, bool expect_failure = false) const;
 
   CompactionReason compaction_reason() const { return compaction_reason_; }
@@ -441,20 +441,20 @@ class Compaction {
 
   static constexpr int kInvalidLevel = -1;
 
-  // Evaluate penultimate output level. If the compaction supports
-  // per_key_placement feature, it returns the penultimate level number.
+  // Evaluate proximal output level. If the compaction supports
+  // per_key_placement feature, it returns the proximal level number.
   // Otherwise, it's set to kInvalidLevel (-1), which means
-  // output_to_penultimate_level is not supported.
-  // Note: even the penultimate level output is supported (PenultimateLevel !=
+  // output_to_proximal_level is not supported.
+  // Note: even the proximal level output is supported (ProximalLevel !=
   // kInvalidLevel), some key range maybe unsafe to be outputted to the
-  // penultimate level. The safe key range is populated by
-  // `PopulatePenultimateLevelOutputRange()`.
-  // Which could potentially disable all penultimate level output.
-  static int EvaluatePenultimateLevel(
-      const VersionStorageInfo* vstorage,
-      const MutableCFOptions& mutable_cf_options,
-      const ImmutableOptions& immutable_options, const int start_level,
-      const int output_level);
+  // proximal level. The safe key range is populated by
+  // `PopulateProximalLevelOutputRange()`.
+  // Which could potentially disable all proximal level output.
+  static int EvaluateProximalLevel(const VersionStorageInfo* vstorage,
+                                   const MutableCFOptions& mutable_cf_options,
+                                   const ImmutableOptions& immutable_options,
+                                   const int start_level,
+                                   const int output_level);
 
   // If some data cannot be safely migrated "up" the LSM tree due to a change
   // in the preclude_last_level_data_seconds setting, this indicates a sequence
@@ -482,10 +482,10 @@ class Compaction {
       InternalKey* smallest_key, InternalKey* largest_key,
       int exclude_level = -1);
 
-  // populate penultimate level output range, which will be used to determine if
-  // a key is safe to output to the penultimate level (details see
-  // `Compaction::WithinPenultimateLevelOutputRange()`.
-  void PopulatePenultimateLevelOutputRange();
+  // populate proximal level output range, which will be used to determine if
+  // a key is safe to output to the proximal level (details see
+  // `Compaction::WithinProximalLevelOutputRange()`.
+  void PopulateProximalLevelOutputRange();
 
   // If oldest snapshot is specified at Compaction construction time, we have
   // an opportunity to optimize inputs for compaction iterator for this case:
@@ -616,37 +616,37 @@ class Compaction {
 
   // only set when per_key_placement feature is enabled, -1 (kInvalidLevel)
   // means not supported.
-  const int penultimate_level_;
+  const int proximal_level_;
 
-  // Key range for penultimate level output
+  // Key range for proximal level output
   // includes timestamp if user-defined timestamp is enabled.
-  // penultimate_output_range_type_ shows the range type
-  InternalKey penultimate_level_smallest_;
-  InternalKey penultimate_level_largest_;
-  PenultimateOutputRangeType penultimate_output_range_type_ =
-      PenultimateOutputRangeType::kNotSupported;
+  // proximal_output_range_type_ shows the range type
+  InternalKey proximal_level_smallest_;
+  InternalKey proximal_level_largest_;
+  ProximalOutputRangeType proximal_output_range_type_ =
+      ProximalOutputRangeType::kNotSupported;
 };
 
 #ifndef NDEBUG
 // Helper struct only for tests, which contains the data to decide if a key
-// should be output to the penultimate level.
+// should be output to the proximal level.
 // TODO: remove this when the public feature knob is available
 struct PerKeyPlacementContext {
   const int level;
   const Slice key;
   const Slice value;
   const SequenceNumber seq_num;
 
-  bool& output_to_penultimate_level;
+  bool& output_to_proximal_level;
 
   PerKeyPlacementContext(int _level, Slice _key, Slice _value,
                          SequenceNumber _seq_num,
-                         bool& _output_to_penultimate_level)
+                         bool& _output_to_proximal_level)
       : level(_level),
         key(_key),
         value(_value),
         seq_num(_seq_num),
-        output_to_penultimate_level(_output_to_penultimate_level) {}
+        output_to_proximal_level(_output_to_proximal_level) {}
 };
 #endif /* !NDEBUG */